#505 null pointer in map.c

[BlueKiller]

Here is the critical code:

…
  iterator=MagickMapAllocateIterator(map);        //510
  while(MagickMapIterateNext(iterator,&key))
  {
const void *object=MagickMapDereferenceIterator(iterator,&size);
…

MagickMapAllocateIterator(…) may return NULL,the “iterator” was passed to MagickMapIterateNext.

in MagickMapIterateNext:

…
MagickExport unsigned int
MagickMapIterateNext(MagickMapIterator iterator,const char **key)
{
  assert(iterator != 0);                            //868
  assert(iterator->signature == MagickSignature);
  assert(key != 0);
…

If iterator is NULL,the assertion "assert(iterator !=0)" will failed.

Credit: ADLab of Venustech

[Bob Friesenhahn]

This is a duplicate of issue #477, which is now fixed.